In industries such as semiconductor processing, pharmaceutical and chemical manufacturing, high purity, highly corrosive and/or highly caustic liquids are utilized. Due to safety and quality considerations, these liquids must be contained in containers and dispensing systems of high reliability and integrity. The connections, tubing, and fittings for handling these fluids must be formed from highly inert materials. Fluoropolymers have been found to be suitable for use in these environments. The tubing is commonly formed of PFA, the fittings, valve components and dispense heads may be formed of components such as PFA and PTFE, and other fluoropolymers. Containers for handling these liquids are typically plastic drums formed of high purity polyethylene such as shown in U.S. Pat. No. 6,045,000 identified as assigned to Fluoroware, Inc., a predecessor corporation of the owner of this invention. Examples of dispense heads suitable for use with these drums are illustrated in U.S. Pat. No. 4,699,298, assigned to FSI Corporation and 5,108,015 identified as assigned to Fluoroware, Inc. The above three patents are incorporated herein by reference.
The drums, will conventionally, have a bung opening with a drum insert that includes a down hole tubing portion connecting to an upward and concentric nipple. A closure fits on the bung and drum insert for shipment or storage of the drum. A dispense head such as those described above, couples with the insert and has a main fluid passageway that connects to and sealingly engages the nipple.
In certain applications it is desirable to automatically cutoff the flow in the main fluid passageway through the dispense head when the dispense head is removed from the drum. This is conventionally accomplished by a centrally located spring-loaded poppet that depresses into an open position when the dispense head is attached to the drum insert. Such poppets close when the dispense head is removed and thus prevents fluid in the dispense head and main tubing line from spilling out when the dispense head is removed. Such poppets will conventionally have an axial engagement portion that contacts a central seating member centrally supported in the male fluid passageway of the insert by a plurality of spokes. This structure allows the fluid to flow between the spokes. Such an arrangement works well mechanically although the spokes and central seating member interfere with and restrict the main fluid flow.
The dispense head will conventionally have a vent for allowing displaced fluid to be replaced by a gas supplied through a secondary tubing that connects to a fitting on the dispense head. The dispense head may also have a seal verification feature. The dispense head will typically have several concentric O-rings that seal to the drum insert and bung. The seal verification feature constitutes a fitting on the dispense head that connects to a closed chamber between adjacent O-rings. The need to have multiple passageways in the dispense head limits the room available for the main fluid passageway and poppet. Thus, flow rates may be less than ideal.
In many applications, the fluid that is dispensed needs to be recirculated to the drum. This is conventionally accomplished by way of a second dispense head on a second bung opening on the drum. Recirculation of fluid often creates foaming which can cause problems such as foam entry into the vent lines and potential clogging or contamination of normally dry areas of the dispense head and gas refill line, and difficulty in emptying a drum with low levels of fluid.
Generally a recirculation feature would be desirable. A higher flow volume would be desirable in a dispense head that provides poppet shut-off control. Where a drum has a recirculation line, an anti-foaming mechanism would be helpful.